You’ve probably seen pictures of it. A massive, circular blemish on the face of Mars that looks like a giant's thumbprint. That’s Olympus Mons. It is the highest volcano in the universe—or at least the highest one we’ve discovered in our solar system, which is basically the same thing when you realize how much empty space is out there. Honestly, calling it a mountain feels like an insult. It's a monster.
Imagine standing at the base. You wouldn’t even see the peak. The curve of the planet would literally hide the summit from you because the volcano is so wide. It’s about the size of Arizona. Not a city. An entire state.
What makes Olympus Mons so ridiculously tall?
It’s all about the plumbing. On Earth, we have plate tectonics. The crust moves around like a bunch of rafts on a lake. When a "hotspot" of magma tries to poke through, the crust moves, and you get a chain of smaller volcanoes like Hawaii. Mars is different. It’s basically a one-plate planet. The crust stayed still for billions of years while a massive plume of molten rock just kept pumping material into the same exact spot.
It’s $21.9$ kilometers high. That is roughly 13.6 miles. To put that in perspective, Mount Everest is only about 5.5 miles high. You could stack two and a half Everests on top of each other and you’d still be looking up at the rim of Olympus Mons.
The gravity helps too. Mars has much weaker gravity than Earth—about 38% of what we feel here. On Earth, a mountain that big would literally crush the crust beneath it and sink. Mars is sturdy enough, and the gravity is light enough, that the volcano can just keep growing and growing without collapsing under its own weight.
The structure of a monster
If you looked at it from above, you’d notice it’s a shield volcano. It’s not a jagged, pointy peak like the Matterhorn. It has a very gentle slope. Usually only about 5 degrees. If you were hiking up it, you might not even realize you were climbing a mountain for the first few miles. But then you’d hit the cliffs.
Around the edge of the volcano is a massive scarp—a vertical cliff face that drops down up to 6 miles in some places. Scientists like James B. Garvin from NASA have spent years looking at these features. Why are there cliffs there? Some think it’s because the weight of the volcano caused the surrounding land to buckle. Others think ancient Martian oceans might have eroded the edges.
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At the very top, there’s a caldera complex. It’s not just one hole. It’s six overlapping craters that make up a giant pit 50 miles wide. It looks like a collapsed honeycomb.
Is it still "alive"?
This is where things get spooky. For a long time, we thought Mars was a "dead" planet. Cold. Quiet. But then the Mars Express orbiter took some high-resolution shots. We found lava flows on the slopes that are only about 2 million years old. In geological terms, that’s yesterday.
There's no reason to think it couldn't erupt again. It probably isn't "extinct," just dormant. Like a giant that’s been napping for a few million years.
The atmosphere at the summit
If you stood at the top, you’d basically be in outer space. The Martian atmosphere is already thin—about 1% of Earth's. But at the top of Olympus Mons, the air pressure is only about 5% to 8% of the surface pressure. You’re above the dust. You’re above the clouds.
Wait. Actually, you aren't always above the clouds.
Sometimes, water ice clouds drift around the summit. It’s one of the few places on Mars where you might see something resembling "weather" in the way we understand it. But don't expect to breathe. You’d need a full-blown pressurized spacesuit just to keep your blood from boiling.
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Why we can't just land there
People ask why we don't just land a rover right in the crater. It'd be cool, right?
Landing on Mars is hard because you need the atmosphere to slow you down. Parachutes need air to catch. Since the highest volcano in the universe pokes so far out of the atmosphere, there isn't enough air to slow a lander down. You’d hit the ground at thousands of miles per hour. It’s a "dead zone" for current landing technology. We have to land in the lowlands where the air is "thick" enough to help us stop.
Comparisons that put it in perspective:
- Width: Roughly 370 miles (600 km).
- Volume: About 100 times the volume of Mauna Loa, the largest volcano on Earth.
- Slope: So gentle you could drive a Honda Civic up most of it.
- Age: Some parts are 3 billion years old, others are much, much younger.
The weird "Aureole" mystery
Around the base of the volcano is a weird, messy terrain called the "aureole." It spreads out for hundreds of miles. It looks like giant ripples or crumpled paper. Geologists think these are the remains of gargantuan landslides. Imagine a chunk of a mountain the size of a country just sliding off and spreading across the desert. That’s the kind of scale we’re talking about here.
It’s hard to wrap your head around. Everything on Mars is built on a scale that makes Earth feel small.
What this means for future explorers
If humans ever colonize Mars, Olympus Mons will be the ultimate tourist destination. But it won't be for the faint of heart. The sheer size of the thing means a trip from the base to the summit would be a multi-week expedition. You'd be traversing a landscape that hasn't changed much since the dinosaurs were walking on Earth.
It also represents a massive opportunity for science. The lava tubes inside the volcano could be miles wide. They could provide natural radiation shielding for habitats. Living inside the highest volcano in the universe sounds like something out of a sci-fi flick, but it’s a legitimate theory for how we might survive on the Red Planet.
How to track Olympus Mons research today
If you're interested in keeping tabs on this Martian giant, you don't have to wait for a person to go there.
- Follow the HiRISE team: The High Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter regularly releases "images of the day." They often capture close-ups of the caldera or the strange landslides at the base.
- Check the Mars Express data: The European Space Agency (ESA) has some of the best 3D topographical maps of the Tharsis region where Olympus Mons sits.
- Use Google Mars: You can actually "fly" over the volcano in 3D right now. It uses real elevation data. Zoom into the caldera and look at the sheer walls—it gives you a much better sense of scale than a flat photo ever could.
The reality is that Olympus Mons is a reminder of how different planetary evolution can be. Just a few tweaks in gravity and plate tectonics, and you get a mountain that defies everything we know about geography on Earth. It’s not just a big hill; it’s a monument to the violent, volcanic past of our neighbor planet.
Actionable Insights for Space Enthusiasts:
To truly understand the scale of Olympus Mons, use a tool like JMARS (Java Mission-primary Analysis and Remote Sensing), which is free and used by NASA scientists. You can layer different types of data—thermal, topographical, and visual—to see how the volcano looks in different spectrums. Additionally, look up the "Tharsis Bulge" to see the three other "smaller" volcanoes (Arsia Mons, Pavonis Mons, and Ascraeus Mons) that sit in a neat line next to Olympus. They are still bigger than anything on Earth, yet they look like pebbles next to the king.